Prevent new server code from returning toolResult

This doesn't impact the ability of clients to handle it (see `Client.callTool`), but does make it a type error to return the old format. This will make it easier to catch sites that haven't been updated.

src/types.ts

@@ -1061,7 +1061,6 @@ export const ServerResultSchema = z.union([
   ListResourceTemplatesResultSchema,
   ReadResourceResultSchema,
   CallToolResultSchema,
-  CompatibilityCallToolResultSchema,
   ListToolsResultSchema,
 ]);